We need support for autoloading modules that implement hardware drivers based on PCI ids.

Currently, it would be used for USB controllers (ohci.mod and uhci.mod), but this autoload support should be extensible so that other drivers for PCI devices can use it in the future.

Autoload should work in a way that drivers are loaded when they're needed, rather than loading all drivers for identified devices automatically. For example, if user loads usb.mod and an OHCI controller is present, ohci.mod should be autoloaded.